Check the exhaust for clogs.  I've seen this on V8's.
             ERic

Jim Arnott wrote:

> Here's the scenario:
>
> 81 Vanagon 2.0 auto.  Came into my life running on three. Nothing in
> the way of compression on #1.  Good friend had a motor with 43k
> original on it.  Swapped motors.  New old motor has 120 +/- on all
> four.  Old old motor sits in shop awaiting teardown.
>
> Drive Vanagon ~2k miles.  Starts easily, runs strong. Uses about a pint
> of 20W50 every 500 miles or so.  No visible leaks, so I assume the it's
> burning it. Sell Vanagon to a good friend. (Who has owned and driven
> many VWs though never a type IV motor. Type I sorta guy.)
>
> Tear down old old motor. (A SIR rebuild with 12k on it.) Find a divot
> out of the #1 piston at the top of the bore.  About 1.5 inches from
> start to end. Looks like maybe it stuck a ring.  Divot extends down the
> side of the piston to the oil control ring. Cylinder head has damage
> equal to what one would expect from compression ring pieces floating
> around. (pictures available) Figure a cylinder and a piston will fix it
> good enough to go in the bay window for a year or so.
>
> A month goes by...
>
> Friend calls from the side of the road.  Go rescue.  Nurse it 70 miles
> home. Pour 2 gallons of oil through it getting it the 70 miles.  Friend
> pulls new old motor and pops the head off.  Guess what?  Exactly the
> same damage on the same hole. Why?
>
> The new old motor had nothing of the old old motor.  Different FI,
> different ECU, different everything. (It was a complete engine.) It was
> not low on oil. It had the correct Bosch plugs and was timed to
> specification. It was a hot day and the failure occurred at the end of
> a long pull. Probably under about the same circumstances as the first
> failure. The other three holes show no sign of detonation or
> overheating.
>
> At this point I'm at a loss.  What would/could cause two identical
> failures on completely different engines? What can we do to prevent
> future failures.
>
> Jim
>
>